This invention relates to machines for guiding cutting or welding torches relative to a pipe.
It is often necessary to cut pipe for joining to another pipe either coaxially arranged therewith or extending at an angle. It has been generally customary for the mechanic to lay out the outline of the cut on the pipe sections, then to cut the pipe by guiding a cutting torch in a freehand manner. Such procedure, however, does not provide the accuracy necessary for a reliable joint and it is usually necessary to further grind or otherwise alter the cut edge to provide an accurate fit before the pipe sections are welded together.
It has also been proposed to provide apparatus for mechanically guiding a cutting or welding torch relative to a pipe in accordance with a pattern or templet carried by the pipe. However, such devices have not been designed to take into account the possibility of inaccuracies in the pipe such as slight bends or undulations or an oval rather than circular cross section. Thus, when the pipe is rotated relative to the tool guiding mechanism inaccuracies are introduced due to the bends in the pipe or its out-of-round section and in some cases where the axis of rotation is not precisely stationary. As examples of such prior art devices, see patents numbered U.S. Pat. No. 2,408,517; 2,459,823; and 3,790,144.